Desulphurized polysulphide polymer and process of making



PATENT- OFFICE DESULPHURIZED POLYSULPHIDE POLYMER AND PROCESS OF MAKINGJoseph 0. Patrick, Morrisville, Pa., assignor to Thiokol Corporation,Trenton, N. J., a corporation of Delaware N Drawing. Originalapplication September 18,

1940, Serial No. 357,230. Divided and this application August 9, 1941,Serial No. 406,167

2 Claims.

This invention relates to organic polysulphide polymers and is adivision of my copending application Serial No. 357,230, filed September18, 1940, which in turn is a continuation-in-part of my applicationSerial No. 28,614, filed June 27, 1935, and Serial No. 168,522, filedOctober 11, 1937.

As set forth in my Patent No. 2,195,380, issued May 26, 1940, and in myapplication Serial No. 267,389, filed April 12, 1939, the organicpolysulphide polymers (which may be produced by reaction betweenalkaline polysulphides and compounds containing two carbon atoms to eachof which is attached a substituent which is split off during thereaction) are, generally, polymers of a unit selected from the group[-i-i-M where represents two adjacent carbon atoms, and

Where pound may have the skeleton carbon structure (where represents twoadjacent carbon atoms) or (where I I I represents two carbon atomsjoined to and separated by intervening structure). X and X are,generically, substituents split off during the reactlon.

Generically therefore these compounds can be defined as having theformulae where the carbon atoms are adjacent and x-ab t-x' I I where thecarbon atoms are joined to and, separated by intervening structure.

The alkaline polysulphides have, generically, the formulae A32 in awhere A is an alkali metal, an alkaline earth metal, ammonium orsubstituted ammonium. Thus the alkaline polysulphide may have theformulae AS2, ASs, AS4, ASs or ASs. Fractional values between theseintegers may be obtained by mixtures. Thus AS221 signifies a mixture ofequal parts of A82 and AS3.

When an alkaline polysulphide having a proportion of sulphur greaterthan corresponds to AS: and represented by 3 to 6 sulphur atoms in themolecule (e. g. an alkaline polysulphide hava formula AS: to a) reactswith an organic compound having the formula as above defined theresulting polymer will be substantially a polymer of the units In theequations and formulae written below the unit is employed but it will beunderstood that in allthese cases the unit t (L I I may be substituted.There is no single acceptable arbitrarysymbol covering both theseskeleton structures and the use of the symbol clearly points out theadvance 'a the art represented by the intervening linkage type ofpolymer over the adjacent carbon atom type. This invention is directedto a generic technique of desulphurization applicable to polymers ofboth types generically or to polymers ofeither type specifically, afterthey have been produced.

Polysulphide polymers may be produced by other than the polysulphidereaction, for example, by reacting a compound having the formula nstJi-sn with an oxidizing reagent, a polymer of the unit is obtained and byreacting this with elementary sulphur polymers of the unit may beproduced.

It has been discovered that said polymers of the unit [-JJ-( S: m a]react with desulphurizing agents according to the equations, forexample,

is in labile form and reacts readily with desulph- 4. To react ades'ulphurizing agent with the polymeric reaction product of an alkalinepolysulphide having the formula AS3 to s and an organic compound havingtwo adjacent carbon atoms to each of which is attached a substituentwhich is split off during the reaction.

Nor is the invention confined to any specific desulphurizing agent. Thereaction is preferably carried out while the polymer is dispersed in analkaline aqueous serum or dispersion medium and when so effected, thedesulphurizing agent is preferably a water soluble alkalinedesulphurizing agent, e. g. an alkaline monosulphide, hydrosulphide,sulphite, hydroxide, hydrosulphite, etc., but numerous otherdesulphurizing agents may be employed.

The polymer both before and after the desulphurizing treatment ispreferably employed and obtained, respectively, in an intermediateurizing agents or substances capable of combining with sulphur and saidlabile sulphur is therefore capable of being removed, in whole or inpart.

It has further been discovered that this complete or partial removal oflabile sulphur causes an improvement in physical properties, e. g.

elasticity and tensile strength.

The objects of the invention therefore include the following:

1. To react polymers of the unit a-M Y 'with a desulphurizing reagent.

2. To react polymers of the unit with a desulphurizing reagent.

3. To react a desulphurizing agent with the 1939 and March 26, 1940,respectively; See eX- amples 2 and 3 of United States Patent No.

2,142,144 and Examples 2, 4, 7' and 9 of United States Patent No.2,l95,380.

The principles and scope of the invention have been explained above andwill be defined in the claims. A specific embodiment of said principleswill be illustrated by the following example:

ExampZa-Jnto a closed reaction tank suitably equipped with stirringmeans, pipe coils forsteam and cold water and a thermometer, are placed2,000 liters of 3-molar sodium tetrasulphide solution. To thepolysulphide solution are added with vigorous agitation, 10 kilograms ofcaustic soda dissolved in 15 liters of Water. This is followed by theaddition of '25 kilograms of crystallized magnesium chloride(MgCl2'.6H2O) dissolved, in 20 liters of water.

The polysulphide mix is heated to about 135 F. and about 700 kilograms(5 kilogram mols) of BB dichlorethyl ether are added gradually over aperiod of about three hours. The rate of addition of the dichloro etheris so regulated as to prevent the temperature from going above about 210F. during the reaction. I

When all the chloro ether has been added and the temperature shows atendency to drop, steam may be admitted to the heating coils and soregulated as to maintain a temperature of from 215 to 220 F. for abo'utthree hours during which time the latex-like dispersion of the polymeris constantly stirred or agitated. The heating step just described iscarried out in order that the excess of polysulphide over that actuallyrequired to decompose the dichlor ether may exert a condensing orpolymerizing effect on the reaction product as first formed.

The finely divided latex-like dispersion of the polymer may now be freedfrom water-soluble impurities by any suitable means, such as filtrationand repeated washing with water, or it may be washed by repeatedsettling of the particles and removal of supernatant liquid, followed byresuspension in clean water and repetition of the settling process. Thewashing produces a purified latex-like dispersion of the polymer whichis now submitted to desulphurization as follows:

Add 250 kilograms (6.25 kilogram mols) of NaOH dissolved in 500 litersof water, raise the temperature to 212 F. and maintain there for about30 minutes. Then cool and purify the resulting latex as above described.

The washed latex-like dispersion may now be used as such or the polymerfrom which labile sulphur has been removed may be separated from thelatex by coagulation or evaporation of the water. Coagulation maybeproduced by rendering the latex slightly acid.

In the above example the polymer prior to desulphurization, is a polymerof the unit and by the action of the NaOH at elevated temperatures ischanged into a polymer of the unit As further specific examples, any ofthe organic compounds listed in Tables 1, 2, '3 and 4 in my UnitedStates Patent No. 2,195,380, on pages 3 and 4 of my United States PatentNo. 2,142,144, and in my applications Serial No. 218,874, filed July 12,1938, now United States Patent N0. 2,216,044, and Serial No. 267,389,filed pril 12,

1939, may be substituted for the dichlorethyl ether of the abovespecific example. Where X orX' or both are directly attached to anaromatic nucleus, the conditions under which the polymer is formed(prior to desulphurlzation) by the polysulphide reaction should be moredrastic as illustrated by Example 8 of my application Serial No.218,874, filed July 12, 1938, now U. S.

' Patent No. 2,216,044, in order to split off the said X and/or Xsubstituents from the aromatic nucleus.

I Among the compounds so listed or those that may be substituted for theBB dichlorethyl ether in the above specific example, the following maybe specifically herein set forth:

ethylene dichloride (and olefin dichlorides in eneral).

Cl.CH2.CH2.O.CH2.O.CH2.CH2.C1

di (beta chlor ethoxy) methane, or di (beta chlor ethyl) formaldehydeacetal.

C1.CH2.CH2.O.CH2.CH2.O.CH2.CH2.C1

di (beta chlor ethoxy) ethane, or di (beta chloro ethyl) ether ofethylene glycol, or beta chlor ethoxy chloro ethyl ether.

C1.CH2.CH2.O.CH2.CH2.O.CH2.CH2.O.CH2.CH2.C1

Where R and R are the same or different alkyl, aralkyl or aryl radicals,

where R R R and R are the same or different alkyl, aralkyl or arylradicals,

where R R and R are the same or different alkyl, aralkyl or arylradicals,

where R R and R are the same or different alkyl, aralkyl or arylradicals.

When polymers made from compounds having the above formulae where R R Rand R are alkyl radicals, are reacted with a desulphurizing agent andsome or all of the labile sulphur thereby removed, the resulting productis found to be greatly improved in respect of tensile strength,elasticity and other desirable qualities, including the ability towithstand low temperatures without serious impairment of elasticity andstrength. The improvement is particularly noted in the polymer when itis heated and cured and thus transformed from the intermediate stage tothe final stage.

Examples of compounds having more than two substituents, which may beused to make a polymer to be subjected to desulphurization are asfollows:

OH.OHz.Cl(l-l,2 trichlor ethane) CLCELCHCLCHLCHLCI (1,2,4, trichlorbutane) CLCHaCHCLCHCLCH Dl (l,2,3,4 tetrachlor butane) CBH3(CH2C1)S(trichlor mesitylene) and other compounds as set forth in my applicationSerial No. 293,090, filed September 1, 1939.

Among the numerous instances which might be cited to illustrate theutility of the present invention and the advantages flowing from its usethe following may be mentioned:

When an intermediate polymer made by reacting sodium tetrasulphide withBB dichlor ethyl ether is compounded with about ten parts by weight ofzinc oxide and sixty parts by weight of carbon black and cured byheating, the rubberlike particles obtained which while possessingnumerous valuable properties including high resistance to a number ofsolvents, has a tensile strength of about 900 pounds per square inch andan elongation at break of about 250%. If

now the labile sulphur is removed from said in termediate polymer beforecuring and the resulting desulphurized or stripped polymer subjected tothe same cure, it will be found that the resulting cured compoundpossesses a greatly increased tensile strength and elongation at break,to wit: about 2,000 pounds per square inch tensile strength and about400 to 450% elongation at break. At the same time the resistance tosolvents has not been decreased and there is a substantial increase inabrasion resistance and general chemical stability. In other words,there is produced a compound having a combination of high tensilestrength, elasticity and stability toward solvents. Such combination ofqualities is highly desirable in a synthetic rubber-like polymer.

Another marked development of new properties is illustrated by the factthat if the stripped polymer, as for example in its cured condition, is

employed to make a structure having a surface which if made from rubberwould generate static electricity by friction and the like, the saidstructure does not develop static electricity and finds use in themanufacture of numerous articles for use where the generation of staticelectricity is undesirable, as for example, guides and rolls employed inthe textile industry which come in contact with silk, cotton,'wool,synthetic fibres, etc. This unique property is developed by the removalof the labile sulphur and is characteristic of the disulphide polymersas distinguished from the polymers having a higher sulphur rank, that isto say, a higher proportion of sulphur in the polymer. This particularaspect of the invention is more fully set forth in allowed applicationSerial No. 125,271, filed February 11, 1937, now

United States Patent No. 2,218,176.

I claim:

1. The process which comprises reacting a desulphurizing agent with thepolymeric reaction product of an alkaline polysulphide having aproportion of sulphur represented by 3 to 6 sulphur atoms in themolecule and BB di (chloroethoxy) ethyl ether.

2. A product substantially identical with that obtained by the processof cl 1. JOSEPH C. PATRICK.

